Air propeller with variable pitch



'July 9, 1935. J. AlVAZ 1 AIR PROPELLER WITH VARIABLE PITCH Filed Jan. 21935 4 Sheets-Sheet 2 0 Q E W Z a J l iulll July 9, 1935.

J. AIVAZ AIR PROPELLER WITH VARIABLE PITCH 4 Sheets-Sheet 5 Filed Jan27, 1933 )NueNToR' .IMIL. A

July 9, 1935.

J. AlVAZ AIR PROPELLER WITH VARIABLE PITCH Filed Jan. 2'7, 1933 4Sheets-Sheet 4 Patented July 9, 1935 UNITED STAT AIR PROPELLER WITHVARIABLE PITCH Jacques A'ivaz, Paris, France Application January 2'1,1933, Serial No. 653,887

In France February 17, 1932 18 Claims.

My invention relates to propellers or to windwheels adapted for brakingpurposes, whose pitch can be varied while in operation and in which thevariation of the pitch is efiected by a mechanism 6 driven from thepropeller driving shaft itself.

' the like.

Other objects of the invention are to devise means whereby the actualpitch of the propeller will be indicated to the pilot, and also meanswhereby the pitch varying device will be dependent upon the altitude orthe engine speed.

With these and other objects in view as will appear from the followingdescription, my invention resides in the combination of parts andprovision of means as will be set forth in said description and morefully pointed out in the claims.

Broadly considered the speed-reducing gear between the propeller drivingshaft and the blades, includes in accordance with my invention, for eachblade, two epicyclic gear wheel trains of contrary and equal or'unequalspeed ratios, and so arranged that an operative connection between thepropeller driving shaft and the blades can be obtained by the medium ofeither train, each of which comprises at least one loose wheel which maybe braked or held in position by a friction device whereby thecorresponding train will be made operative, said loose wheels beingpreferably common to the various gear wheel trains associatedrespectively with the various blades.

Various embodiments of such gear and of devices designed to attain theother objects above set forth are illustrated by way of example in theannexed drawings in which:

Fig. l is a lengthwise section of a mechanism in conformity with theinvention;

Fig. 2 is a section of a modification;

Fig. 3 is a lengthwise section of a pitch-indicating mechanism;

Fig. 4 is a section on the line 4-4 of Fig. 3;

Fig.5 is a section of a mechanism for actuating the brakes of the loosewheels;

Fig. 6 is a vertical section, on the line 8-6 of Fig. '7, of a mechanismby which the brake mechanism for the loose wheels is made dependent uponthe engine speed;

Fig. 7 is a section on the line 1-1 of Fig. 6;

FlFigl. 8 is a partal section entire line 8-8 of 8- F-uFig. 9 is apartial section on the line 9-8 of Fig. 10 is a view of thecorresponding pitch-indicating mechanism;

Fig. 11 is a view of a mechanism peculiar to each blade for rotating thelatter.

In the form of construction shown in Fig. 1, the driving gearing whichconnects the propeller 10 shaftl to-each blade carrier 2, chieflycomprises, in peripheral disposition, a plurality (two, three or more)of sets of three epicyclic gear wheel trains. In each set, the planetarypinions 3, 3a, 3b, of the different trains are connected with 15 oneanother in such manner as to be subjected to a common planet movement,and for this purpose they are'mounted for instance upon a common stud 4secured to two plates 5. The planetary pinions 3 engage on the one handa 20 common gear wheel 6 which is concentric with the shaft I androtates with this latter, and on the other hand a toothed ring I whichis secured to the casing. In these conditions, the

aggregate consisting of the plates 5, the studs 25 4 and the differentplanetary pinions 3, Math, will be rotatedabout the axis of the shaft inthe same direction as the latter but at less speed.

"The planetary pinions 3a and 3b respectively gear, on the one hand,with the loose toothed rings 8a: and 8b, and on the other hand, withteeth 9a and 9b formed on a sleeve l0 mounted loose on the propeller hubI l. The rings Ba. and

-8b are loosely rotatable, but may be held in place at will, and withall the desired gradual move- 35 ment, by a suitable braking device, ofwhich only the facings in and H17 are represented. Various embodimentsof actuating means for the braking device will be described hereinafter.Furthermore, the diameter of the planetary pin- 40 ion 3 lies betweenthe diameters of the planetary pinions 3a and 317. Hence the ratios ofthe epicyclic trainsB, 3, I, 80., 3a, 911, I3, l4, and 6,3, 1, 8b, 3b,917, I3, it are in the contrary sense.

The aforesaid speed-reduction gearing serves 45 to drive the turningmechanism affording the angular displacement of the propeller blades. Inthe construction herein represented, each propellerblade is providedwith its own direct turning mechanism and these latter, the same in 50number as the blades, are geared to the sleeve Hi.

It will be observed that therein the device comprises only two loosewheels 8a and 8b, which are common to .all the blades. Obviously, theconnection between the blades and the sleeve I0 blades turningmechanisms.

.ll mounted on the sleeve II and engaging a pinion is, for each blade,which is keyed to a shaft l5 which imparts the motion to thecorresponding turning mechanism, and which rotates in bearings IIsecured on the shaft I.

An embodiment of a turning mechanism peculiar to each blade will behereinafter described.

The device adapted to prevent all improper operation of thepitch-varying mechanism, herein consists of a friction device adapted tobrake each shaft l5 and comprising the parts l8 to 22.

The operation of the said driving gear is as follows;

The mechanisms for turning the propeller blades, as well as the pinionsII, are carried by bearings mouniid on the rotary casing of thepropeller, and hence they participate in the rotation of the propeller.On the other hand, the resistance of each propeller blade to angulardisplacements about its axis is such that the pinions [6 can only berotated on their axes by a great tangential stress. In these conditions,when therings or sun wheels 80. and 8b are loose, thus preventing anydriving stress from being imparted to the pinions I l, there will be norelative displacement of said pinions nor of the wheel i3, and hencethis wheel will be rotated about its axis at the same speed as thepropeller. This rotation, combined with the rotation of the discs 5carrying the planetary pinions, will impart to the rings or sun wheels8a and 8b different resulting speeds, depending upon the driving ratiosemployed.

When the pilot desires to vary the pitch of the propeller, he throws onone of the brake facings He or l2?) in order to brake or stop thecorresponding ring 8a or 8b. If he should thus hold the ring 80.corresponding to the planetary pinion 3a having the maximum diameter,this pinion will rotate the sleeve ID in the same direction as the shaft8, but at a greater speed. This will produce a relative motion of thewheel 13 with reference to the propeller, and hence with reference tothe pinions l4 secured to the propeller casing, so that said pinions I4will be rotated on their own axes. This will cause the shafts ii torotate and will actuate the By stopping or braking the other ring 8bcorresponding to the planetary pinion 322 having the minimum diameter,this will cause in like manner the rotation of the pinions M on theiraxes, but in a direction contrary to the preceding.

Indicating device of the actual pitch (Fig. 1)

The pitch varying gear is preferably completed by a mechanism by whichthe pilot may know the actual value of the pitch. For this purpose, amember whose position is variable according to the pitch of thepropeller is connected by a suitable driving gearing with an indicatingdevice which is visible to the pilot. In the embodiment shown in Fig. 1,the said member having a position which depends upon the pitch consistsof a ring-shaped nut 21 provided with an annular groove 28in which isslidably engaged the head of a pivoted lever 29 connected on the otherhand to an indicating device not shown, for instance by a rod 30. Thenut- 21 is mounted on a threaded appendage of the wheel l3 or upon alike part adapted to rotate together with the sleeve III, in such mannerthat it may be screwed either way in the case of a relative displacementbetween the wheel I! and the shaft I, and according to the direction ofthis displacement. For this purpose, the nut 21 is connected with amember 3| having the some movement of rotation as the propeller, and insuch manner that it will positively participate in the rotation of saidmember 2|, but may move lengthwise with reference to this latter. Thusthe said member Il may be directly secured to the rotatable propellercasing, or it may be mounted loose on the sleeve III, as shown, and berotated by sets of epicycloidal gears 32, l3, l4 analogous to thetrains], I, 6, the planetary pinions 32 being carried by the studs 4.

In these conditions, any movement of the wheel I! with reference to theshaft I, which corresponds to a variation of the propeller pitch, willcause a lengthwise movement of the nut 21 to a corresponding degree.

Modified construction of the pitch varying gear (Fig. 2)

In the modified embodiment of the pitch varying gear shown in Fig. 2,the wheels 8a and 82), cooperating with braking means by which they canbe stopped, are as before, common to the different blades, but they gearwith common planetary pinions 40, the wheel 8a by means. of internalteeth, and the wheel 8b, by external teeth, so that the speed ratios ofthe two resulting wheel trains have still contrary algebraic signs. Tothe planetary pinions is imparted a planet movement about the axis ofthe propeller, and for this purpose, each pinion is for instance carriedby a shaft journaled in the blade carrier 38. Herein, the number ofplanetary pinions is the same as that of blades, and each pinion ismounted on an extended part of the shafts IS. The movement of theplanetary pinions on their own axes is imparted to the shafts l5 by anysuitable mechanism, and for instance, as herein represented, themovement of each planetary pinion 40 can be imparted to thecorresponding shaft l5 by means of epicycloidal reduction gearing. Forthis purpose, to each shaft I5 is secured a member 35 carrying planetarypinions 38 which herein consist of spur gear wheels, but bevel gearwheels might also be employed. The said pinions 36 gear on the one handwith an external toothed ring 31 secured to the casing 38 which rotateswith the shaft I, and on the other hand, with an internal toothed ring39 which is loose upon the end of the propeller shaft l5 andparticipates in the rotation of the corresponding pinions 40. The devicefor preventing an undesired operation of the pitch varying mechanism,herein consists of a friction device connecting the two rings 8a and 8btogether and comprising the elements 43 to 48.

' The operation is as follows. When the rings 8a and 8b are not braked,the aforesaid gear has no internal motion, due to the resistance offeredby each shaft l5 to all rotation on its own axis, and thus the wheels 8aand 8b will rotate loosely. The ring 31, driven by the casing 38,rotates about the axis of the shaft l together with this latter and withthe blades 2. The shafts l5 of the several blades are stationary asregards motion about their own axes. when one of the rings 8a or 8b isbraked, the respective pinions 40 of the blades 2 will rotate on theiraxes, thus drivingby the medium of the pinion 39-the planetary pinions36. These latter will thus roll upon the ring 21, hence rotating theshaft IS in a direction depending upon the braking of the ring 8a or ofthe ring as. Thering which is not braked will rotate loosely, it beingdriven by the pinion 40. It will I blades is the greatest.

This last-mentioned feature may obviously be employed with equalfacility by the use of the device shown in Fig. l. Modification of thepitch-indicating device This modified form, which can be employed withany pitch varying gear, is characterized by the fact that the indicatorprovided with a pointer, which is visible to the pilot and enables himto know at all times the position of the propeller blades, is controlledby the medium of two different gears one of which is driven from one ofthe rotating parts of the engine, such as the coupling for the usualspeed counter and the other from one of the parts of the pitch varyinggear whose motion is in relation on the one hand to the rotation of themotor and on the other hand to the positive motion given to the blades,and for instance, with one of the rings in or 8b.

The pitch-indicating device, which is shown by way of example, in Figs.'3 and 4, essentially comprises a differential device. The toothed ring54 of thedifferential device is driven from one of may be separate fromthe case'containing the pitch indicator, and may be incorporated in thepitch-varying gear ,or;in the automatic control mechanism, as willbefurther set forth. Herein,

the coupling II is connected with the pitchvarying mechanism, for

instance by a flexible shaft or the like.

control'devtce for the braking of the rings In:

and at (Fi 5) The-facings 12c and lib (Figs. 1 and 2) form part of anyknown braking device, which may comprise brake-shoes, brake-bands or thelike, and the facing carriers can be actuated by any suitable means butit is convenient to connect them togeth'er so that they can be actuatedby .one and the same control device. A preferred embodiment of such adevice is illustrated in Fig. 5 in which the facing carriers are pivotedat one end and actuated from a common shaft 10 by the medium ofinversely disposed crank like members 1|, 1 la, in such a manner thatone facing only can be applied at a time on the corresponding wheel. Anydesired means may be used to simultaneously rotate the crank likemembers 1|, lia but particularly suitable means consists, as shown, in atoothed sector 12 pivotally mounted about the same axis as the cranks,rotatable therewith and in engagement with a reciprocable the parts ofthe motor by means of a coupling connection 55; the toothed ring 58 isactuated by the ring 8a or 8b by means of a coupling connection 51,either directly or by means of-intermediate gearing 58, 59, 60, iii, 62in gear with the rings 54 and 56. The planetary pinions 53,

'5 position which corresponds on the dial 68 to the value of thepropeller pitch.- When the pitch of the propeller is being changed, thering 8a or 8b which remains stationary or whose motion is increased inspeed with reference to the speed of its motion when the pitch remainsconstant, im-

parts this variation of motion to the correspondthe rings 54 and willrotate at different rates, thus effecting an angular displacement of theshaft 54 in the same direction as the ring which has the greater speed.The pointer 61 is thus displaced until the pitch again becomes constant,that is, when the operation of varyingthe pitch has terminated. In thismanner, the pointer shows the actual value of the, pitch.

In particular, this device may consist of a cam 59 (Fig. 3) whichis'mounted on the shaft of the pointer 61 and controls the deliverypower fluid to the engine, in such manner as to throttle this delivery,when. the propeller pitch value comes rack 13. In the embodimentillustrated the crank like members consist of appendages of the sector12 to which is pivoted one end of each facing carrier, the pivotconnections being so located that by turning the sector 12 in eitherdirection out of the middle position here shown, one facing will beapplied against the cooperating wheel while the other facing is movedaway from the other wheel.

. vThe rack 13 may be actuated by any convenient means and the hydraulicdevice illustrated in Fig. 5 is given solely as an example. In thisdevice, the rack 13' is secured to a piston 14 movable in a cylinder. 15provided at each end with condults 18 and 19 leading to a four-way cocksituated within reach-of the pilot or controlled at a distance, andconnected on the other hand with a source of fluid under pressure, suchas the lubricating oil of the motor, and with a suitable dischargechamber or receptacle.

Thus the fluid under pressure can be caused to act on either side of thepiston 14, thereby moving the latter and the rack 13 in one direction orin the other, from the middle position illustrated.

Governing-device for making the pitch-varying year dependent upon thespeed of the motor An improvementin the pitch varying gear abovedescribed'consists in providing it further with a regulating device orgovernor by which the brakes will be operated, with or without theinterposition of a servo-motor, such governor being optionally under thecontrol of the pilot. In this way, the pitch of the propeller will beVaried automatically according to the altitude, or in short, accordingto the speed of the motor.

Such governing device will essentially comprise a centrifugal governorof any known type driven by the engine by means of suitable gear, and itoperates the brake actuating means either directly or by the medium ofpower means of any known type, whether mechanical, hydraulic orelectric. I

An embodiment of such a governing device is illustrated by way ofexample in Figs. 6 to 10.

In this embodiment a centrifugal governor including the weights 8!acting. through a plate 88 on -a two arm lever pivoted on a stud 88 isdriven from! the engine by means of the shaft 85 the bevel gear wheels88 and 85, the friction coupling 83 and the spur wheel 88, looselymounted on a shaft ll carried by a casing 82. The brake operating meansincludes for instance, a movable member responsive to a fluid underpressure and a control valve, as above described in connection with Fig.5, such control valve is actuated by the centrifugal governor by meansof the lever 88. Fig. 9 distinctly shows a combination of means for thispurpose. n the stud 88 is keyed a lever 9| the other end of which ispivoted at 82 on the valve-piston slidable in a valve-cylinder providedwith ports 84 and 85 respectively connected to the conducts l8 and 18leading into the cylinder 15 and within an inlet port 95 connected tothe source of fluid under pressure and with discharge ports 81 connectedto the discharge receptacle. The piston 88 is peripherally provided withrecesses and the whole acts as a four-way cock, simultaneouslyconnecting the inlet, 88 with any one of the ports 88, 85 and the secondwith one of the discharge ports 81, or pre-' venting all communicationbetween any two of the aforesaid ports.

The position of equilibrium, fora given speed of the motor and of thecentrifugal governor,

can be modified by the action of an antagonistic spring 88 (Fig. 6)which is so arranged that its action can be modified by the pilot atwill, by means of a suitable device, optionally reversible, which actsthrough the medium of a rod 98.

When the pitch-indicating gear is not contained within the box carryingthe dial visible to the pilot, it is preferably mounted in the casingwhich contains the aforesaid governing device. Herein, the ring l'of thedifferential mechanism of the type represented in Fig. 3 is actuatedfrom a distance by the pitch-varying mechanism, by means of theconnection 55 (Fig. 10). The ring 58 is actuated, through the medium ofthe gearing 82, SI, 58, 59, by a ring 58, secured to the ring 88, whichis driven by the motor.

Blade-turning device (Fig. 11)

This mechanism, which is independent of the manner in which it' isactuated by the engine shaft, is essentially characterized by the factthat it comprises an automatic clutch device, arranged in such mannerthat the power transmission from the engine shaftwill be automaticallycut off at each end position of the blades.

The said mechanism preferably comprises, as herein represented, a deviceconsisting of a stationary screw I8l, and a nonrotatable nut Ilsslidable along the said screw, thus making the driving gear quiteirreversible and increasing the speed reducing ratio. For this purpose,a differential screw might also be employed. The nut I82 is pref rablyconnected with the blade by a rack I83 mounted-on the nut I82 andengaging a toothed sector I88 secured to the arm 2 carrying the blade.The screw IN is loose on the shaft I5 which is driven as above setforth, and a coupling device I85, provided with a spring I85, by whichthe shaft I 5 may be connected with the screw IN, is mounted at each endof the screw. The coupling devices may be of any suitable type, forinstance with clutch teeth, and each device comprises a projection I 81situated on the path of the nut I82 and between this nut and thecorresponding spring I88, and hence the spring will be compressed by thenut when this latter reaches the end of its stroke on one side or theother,.thus eflecting the automatic unclutchins.

It will be noted that the device providing for irreversible action ismounted against the blades. and that the wear can be taken up by varyingthe distance between the axis, for instance by means of an eccentricring I88 mounted around the ball bearings.

What I claim is:

1. In a variable pitch propeller mechanism comprising a plurality ofblades, a driving shaft for rotating said propeller, means forsimultaneously varying the pitch of said blades and means for holdingthe pitch after change, said pitch varying means including two epicyclictoothed wheel trains having speed reducing ratios of oppositealgebraical signs, each train comprising planetary means rotated independence on the propeller rotation and a sun wheel coaxial with saidshaft and rotatable relative thereto, so that said sun wheels normallyrotate with the propeller, braking means cooperating with said sunwheels to produce relative rotation between both said sun wheels ineither direction, and pitch holding means consisting in friction meansnormally restraining said epicyclic trains against any differentialmotion, 1. e. atleast when said braking means are out of application.

2..In a variable pitch propeller mechanism comprising a plurality ofblades, a driving shaft for rotating said propeller, means forsimultaneously varying the pitch of said blades and means for holdingthe pitch after change, pitch varying means'including two epicyclictoothed wheel trains having speed reducing ratios of oppositealgebraical signs, each train comprising planetary means rotated independence on the propeller rotation and a sun wheel coaxial with saidshaft and rotatable relative thereto, so that said sun wheels normallyrotate with the propeller, braking means cooperating with said sunwheels to produce relative rotation between both said sun wheels ineither direction, and pitch holding means consisting in friction meansaffording a friction coupling directly connecting together both saidcoaxially disposed sun wheels.

3. In a variable .pitch propeller mechanism comprising a plurality ofblades, a driving shaft for rotating said propeller, means forsimultaneously varying the pitch of said blades and means for holdingthe pitch after change, two epicyclic toothed wheel trains having speedreducing ratios of opposite algebraical signs, each train comprisingplanetary means rotated in dependence on the propeller rotation and asun wheel coaxial with said shaft and rotatable relative thereto, sothat said sun wheels normally rotate with the propeller, friction meansnormally restraining said epicyclic trains against differential motion,means for momentarily and selectively varying the rotation resistingload on said sun wheels to produce difference between said resistingloads and thereby a differential motion and means responsive to suchdifferential motion for moving the bladesto vary the pitch thereof.

4. In combination with an air screw propeller with variable pitch, pitchvarying means, an engine for rotating said propeller, a governorresponsi e to the engine speed and controlling said pitch varying meansto automatically cause a pitch variation in response to a variation -inthe engine speed and adjusting means actuatable at will during operationof the governor to vary will the end engine speeds-allowed.

5. a variable pitch propeller mechanism com ing a plurality of blades, adriving shaft for rotating said propeller and a pitch varying gearadapted to afford an operative connection between said shaft and thevarious blades to vary the pitch thereof, a pitch varying gearincluding. two speed reducing epicyclic' toothed wheel trains, a sunwheel of each train being coaxial with said shaft and rotatable relativethereto and carrying gear teeth provided externally on one wheeland'internally on the other,

a planetary pinion in mesh with both said teeth,

means for rotating said pinion around the driving shaft in dependence onthe propeller rotation, means for momentarily producing a difference inthe rotation resisting loads on said sun wheels whereby producing arotation of said pinion about its own axis, and means responsive to thisrotation of said pinion for moving the blades where'- by varying thepitch thereof.

6. In a variable pitch propeller mechanism a 'pitch varying gear as inclaim 5 wherein further the means responsive to the rotation of theplanetary pinion for moving the blades includes a second speed reducingepicyclic train comprising two sun wheels and at least one planetarypinion, one sun wheel being solid with the planetary pinion of the firstnamedepicyclic train,

.means stationarily securing the other sun wheel to the propeller, aplanet carrier rotating with the propeller and means responsive to therotation of said planet carrier about its own axis for moving the bladeswhereby varying the pitch thereof.

'7. In a. variable pitch propeller mechanism comprising a plurality ofblades, a hub for supporting said blades and a pitch varying gearincluding a rotatable screw-threaded member stationary carried by thehub and anon rotatable but lengthwise shiftable screw-threaded member inmesh with the preceding one, said members being located close to theblade, and a motion transforming contrivance operatively connecting saidendwise movable member to the blade to transform a linear endwise motionof said member into an angular motion of the blade, such contrivancecomprising strictly the requisite number of members for performing suchtransformation without any non motion-transforming gearing member.

8. In a variable pitch propeller mechanism comprising a plurality ofblades, a hub for supporting said blades and a pitch varying gear, saidpitch varying gear including a plurality of sets of a stationary androtatable screw carried by said hub and of a non rotatable butlengthwise shiftable nut in mesh with said screw, each set beingassociated to a corresponding blade and located close to said blade, anda motion transforming contrivance operatively connecting said nut to theblade to transform the linear endwise motion of the nut into an angularmotion of the blade, suchcontrivance comprising strictly the requisitenumber of members for performing such transformation without any nonmotion transforming gearing member. p

9. In a variable pitch propeller mechanism pitch-varying gear as inclaim 8, wherein further said motion transforming contrivance includes arack solid with the endwise movable member and spur wheel teeth rigidlycarried by the blade and comprising a plurality of blades, 9. drivingshaft for rotating said propeller and a pitch'varying gear adapted toaiford an operative connection between said shaft and the various bladesto vary the pitch thereof, said pitchvarying gear including twoepicyclic toothed wheel trains having speed reducing ratios of oppositealgebraical signs, each train comprising planetary means rotated independence on the propeller rotation and a sun wheel coaxial with saidshaft and rotatable relative thereto, so that said sun wheels normallyrotate with the propeller, friction means normally restraining saidepicyclic trains against diil'erential motion means for momentarilyandselectively varying the rotation resisting load on said sun wheels toproduce difference between said resisting loads, and thereby adifferential motion, plucomprising a plurality of blades, a hubhaving a.socket for carrying said blades, a driving shaft for rotating saidpropeller and a pitch varying gear, said pitch varying gear including ascrewthreaded shaft rotatably journaled in said socket about an axisparallel to the hub axis and stationary with respect to the hub, a nutlongitudinally movable onv said shaft, rack teeth rigidly carried bysaid nut, spur wheel teeth rigidly provided on the blade and in meshwith said rack and gearing means adapted to rotate said shaft incontrary directions.

12. In a variable pitch propeller mechanism, comprising a plurality ofblades, a hub for carrying. said blades and a pitch varying gear, saidpitch varying gear including a plurality of nut and screw contrivancesassociated respectively with the various blades, one element of eachcontrivance is stationary and rotatable and the other non rotatable butendwise shiftable, a plurality of motion transforming contrivances eachof which operatively connects one of said endwise movable members to theassociated blade to trans-. form a, linear motion of said member into anangular motion of the blade and meansadapted to simultaneously rotatethe rotatable members of the various nut and screw contrivances, suchmeans including two epicyclic toothed wheel trains normally frictionablyrestrained against differential motion and means for momentarilyand-selectively producing a differential motion of one train in adirection and of the other in the opposite one.

13. In a variable pitch propeller mechanism comprising a plurality ofblades, a hub for carrying said blades and a pitch varying gear adaptedto move said blades to vary the pitch thereof, said pitch varying gearincluding two toothed wheel trains having speed reducing ratios ofopposite algebraical signs and including an epicyclic gear, each of saidtrains having planetary means rotatable about an axis fixed with respectto the hub and a sun wheel of each train being coaxial with said hub androtatable relative thereto, friction means normally restraining saidepicyclic trains against differential motion, means for momentarilyproducing a differential motion of either train and means responsive tosuch differential motion for angularly moving the blade.

14. In a variable pitch propeller mechanism comprising a plurality ofblades, a hub for carrying said blades and a pitch varying gear adaptedto move said blades to vary the pitch thereof, said pitch varying gearincluding two toothed wheel trains having speed reducing ratios ofopposite algebmical signs and normally frictionally restrained againstdiiferential motion, each train including an epicyclic gear havingplanetary means rotatable about an axis ilxed with respect to the huband asun wheel coaxial'with said hub and rotatable relative thereto,means for momentarily and selectively ying the rotationresisting loadson said sunwheels to produce difference between said resisting loads,and means responsive to a diflerential motion of either train forangularly moving the blade.

15. In a variable pitch propeller a pitch varying gear as in claim 7 andwherein said motion transforming contrivance includes a rack solid withthe endwise movable member and spur wheel teeth rigidly carried by theblade and in mesh with, said rack, and means for bodily moving saidendwise movable member transversely of the blade axis for adjustment ofthe rack and spur wheel engagement.

16. In a variable pitch propeller mechanism comprisng at least oneblade, a hub for carrying said blade and a pitch varying gear adapted tomove said blade 'to vary the pitch thereof, said pitch varying gearincluding a screw-threaded shaft parallel to the hub axis, a nutlongitudinally movable on said shaft, rack teeth rigidly carried by saidnut, spur wheel teeth rigidly provided on the blade and in mesh withsaid rack, bearing means stationary carried by the hub and supportingone end of said shaft both for rotation of said shaft about its own axisand for pivoting motion at least in a plane perpendicular to blade axis,other bearing means stationary carried by the hub and supporting theopposite end of said shaft for rotation of said shaft about its own axisand including an excentric ring surrounding said shaft and angularlyadjustable about its own axis.

17. In a variable pitch propeller mechanism comprising at least oneblade, a hub carrying said blade and a pitch varying gear adapted tomove said blade to vary the pitch thereof, .said pitch varying gearincluding a rotatable screwthreaded member stationary carried by the huband a nonrotatable but lengthwise shiftable screw-threaded member inmesh with the preceding one, a motion transforming contrivanceoperatively connecting said endwise movable member to the blade totransform a linear endwise motion of said member into an angular motionof the blade, means adapted to transmit rotation to said rotatablemember, such means includng one-way clutches disposed respectively andinversely at each end of the rotatable member to drive the latter incontrary directions, and means responsive to the blade angularadjustment for'automatically unclutching the actual driving clutch foreach end position of the blade.

18. In combination with an air screw-propeller with variable pitch,pitch varying means, an engine for rotating said propeller, a governorresponsive to the engine speed and controlling said pitch varying means,to automatically cause a pitch variation in response to a variation inthe engine speed, such governor consisting in a centrifugal regulatorincluding rotatable flying weighted parts driven in dependence on theengine speed, resilient means urging said flying parts in counteractionto the flying force on said parts and means for more or less energizingat will said resilient means while said weighted parts are rotating.

JACQUES AIvAz.

